Disorganised sects are in opposition (10)
I believe the answer is:
resistance
'opposition' is the definition.
(I know that opposition can be written as resistance)
'disorganised sects are in' is the wordplay.
'disorganised' indicates an anagram.
'sects'+'are'+'in'='sectsarein'
'sectsarein' is an anagram of 'RESISTANCE'.
(Other definitions for resistance that I've seen before include "fighters in wartime" , "Freedom fighters - it's measured in ohms" , "Withstanding" , "Rebellious group" , "Rebels" .)